Total Pageviews

Monday, September 10, 2012

Genes, memes and obesity

I
have blogged several times about the uniqueness of obesity to the human race.
Notwithstanding the fact that we share 98% of our genes with our nearest
biological relatives, the chimpanzees, we alone get fat. It therefore follows
that our obesity has origins in the basic biology of energy metabolism and
storage but that it also has origins in the society we have constructed. For hard-nosed
reductionist biologists, sniffing around the causes of obesity outside the
laboratory is most unattractive because it brings us into the world of
psychology, of human behaviour and of social organisation and these are all
seen as “soft sciences”. If this view persists, then the so-called ‘hard
sciences” of genetics and its associated disciplines, will wane in importance. Consider
the brouhaha that greeted the discovery of cafeteria feeding of rats to induce
obesity, the discovery of genetically obese rodent models, the incredible
discovery of the appetite regulating plasma protein leptin and now, the flavour
of the month, the gut microbiota. All have hit the front covers of Nature and
Science and all have been the flavour of the months at key scientific
conferences. But when all of these are added up, the best they can do is
explain bits and pieces of the “how” of obesity. They cannot some of the “why”
such as genetic predisposition but they cannot explain the “why” of individual
obesity and overweight.

What
makes humans so different from other species is that we alone have mastered the
ability to learn from one another by imitation. This imitation can be vertical
such as what we learn from our parents. It can be horizontal such as what we
see others doing. Of course, we actually don’t have to see others doing
something to imitate it. A third party can describe what he or she saw and we
can have a shot at it, maybe getting it right first time, maybe having to go
back for another look at the person who has mastered this act and eventually,
we will be able to do it. These acts of imitation spread through society at a
rate vastly greater than that of natural selection of genetic potential. To the
biological scientist, this is interesting but seriously wooly. It is poorly
defined, poorly characterised, impossible to measure and impossible to
attribute origins of imitated acts.

In
1976, Richard Dawkins wrote a book which to this day remains a best seller
entitled the ‘Selfish Gene’. Dawkins did not mean that there was a gene for
selfishness but rather that all genes were utterly selfish in competing with
other genes to be included in the blue print of the next generation, the one
after that and so on. The human body is the vehicle and the gene is the
“replicator”. But Dawkins stepped boldly out of biology in coining the term
‘meme” to explain the basic unit that is involved in the vertical and
horizontal transmission of human knowledge. The exact quote is thus: “ We need
a name for a new replicator, a noun that conveys the idea of a unit of cultural
transmission, or a unit of imitation.
‘Mimeme’ comes from a suitable Greek root, but I wanta monosyllable that sounds a bit like ‘gene’. I hope my
classicist friends will forgive me if I abbreviate mimeme to meme[1]”.

A
meme is any concept or idea that is replicated by imitation. It can be verbal
(rote, word-of-mouth, sung or chanted), written (prose, verse or music) and it
can be an action (the Maori Haka, the handshake, the Christian blessing). The
private thoughts and fantasies you have lying in bed or day dreaming on the bus
to work are not memes since there is no expectation of transmission to others.
Dawkins saw memes as being identical to genes in their characteristics with the
three prerequisites of the latter: replication, variation and selection. Memes
compete with one another for retention within our brains and there are far more
meme than there is storage space in our brainsfor them so the memes that win out to to be transmittedvertically are no different from the
genes that win out for retention in the next generation.

The
development of obesity is a passive event over time since nobody really sets
out to gain weight. But once we gain weight, we access memes that are implanted
in our brains: “Fat isn’t pretty”; “Being fat is bad for health”. But when it
comes down to the decision to “do something”, what is the behaviour we imitate?
For some, especially among young professionals, the imitated behaviour fights
the passive gain in weight, a life-time commitment of watching and weighing, of
eating carefully and of exercising diligently. This behaviour is also true for
some who lost weight and who want to imitate that behaviour that retains weight
loss. For others, and it is a fact of life that it is the majority, the
imitated behaviour is to do nothing. The meme to do something about overweight
has to compete with memes that govern other activities in daily life and the
modeled meme is one of the status quo. Fat people don’t die on the streets.
They grow old. They are no sadder and no happier, no poorer and no richer and
no more loved or feared than lean people.

The
future of cell biology will reside in the cell since the latter is the raison
d'être of cell biology. Human obesity can be studied by the geneticists and the
memeticists on different planets as is presently the case. Those who bring
these disciplines together will be the future. Memes are neither angels nor
demons, which flit around some unique ethereal space entering our head for good
or bad. Memes are ultimately connected to a neuronal network in the brain,
unique to that meme. Thus they do have a biological base but not a genetic
base. The biological base must connect to the phenotype. I wish I could sing
like the late Luciano Pavarotti or swing my golf club like Tiger woods but I
cant. Why not? I can cut the grass and I’m good at figuring out complex scientific
concepts and at designing experiments to test these theories. Why so? Is our
phenotype where our genotype meets our ‘memotype’? Complex questions indeed but
valid complex questions.

[1]
For those of you who would like a quick tour of memes, try the review by
McNamara in Frontiers of Evolutionary Neuroscience May 2011 (volume 3): “Can we
measure memes”. For a truly fantastic introduction to memes, buy Susan
Blackmore’s book “the Meme Machine”, Oxford University Press.

Translate

"Ever seen a fat fox ~ Human obesity explored"

About Me

I graduated from University College Dublin in 1971 with an Masters in Agricultural Chemistry, took a PhD at Sydney University in 1976 and joined the University of Southampton Medical School as a lecturer in human nutrition in 1977. In 1984 I returned to Ireland to take up a post at the Department of Clinical Medicine Trinity College Dublin and was appointed as professor of human nutrition. In 2006 I left Trinity and moved to University College Dublin as Director of the UCD Institute of Food and Health. I am a former President of the Nutrition Society and I've served on several EU and UN committees on nutrition and Health. I have published over 350+ peer reviewed scientific papers in Public Health Nutrition and Molecular Nutrition and am principal investigator on several national and EU projects (www.ucd.ie/jingo; www.food4me.org). My popular books are "Something to chew on ~ challenging controversies in human nutrition" and "Ever seen a fat fox: human obesity explored"